- Nitrogen-doped cobalt nanocatalysts for carbonylation of propylene oxide
-
Nitrogen-doped cobalt nanoparticles loaded on porous supports were developed for ring-opening carbonylation of propylene oxide. The catalysts were prepared by simply pyrolysis of Co(OAc)2/phenanthroline and supports. As proved by XPS combined with XRD and TEM characterizations, a higher amount of available Co-N sites were responsible for promoting the carbonylative activity. The selectivity of carbonylated products reached 93 percent, which is comparable to previously reported cobalt carbonyl catalysts. The novel type of carbonylative catalyst also could be reused and revealed fine stability due to the continuous generation of active [Co(CO)4]? species during reaction.
- Chen, Lin,He, Lin,Xia, Chungu,Yang, Bingxiao,Zeng, Bo,Zhu, Gangli
-
-
Read Online
- Novel pyridinium based cobalt carbonyl ionic liquids: Synthesis, full characterization, crystal structure and application in catalysis
-
Through an optimized synthetic strategy, a series of novel alkylpyridinium cobalt tetracarbonyl salts, [C1Py][Co(CO)4] (2a), [C 4Py][Co(CO)4] (2b) and [C16Py][Co(CO) 4] (2c) (CnPy = N-CnH2n+1- pyridinium), were successfully prepared in good yields, using a water-organic biphasic system. All the three compounds melt well below 100 °C and could be classified as ionic liquids. The compounds were fully characterized using IR, UV-Vis, 1H NMR, 13C NMR, ESI-MS and elemental analysis, and 2c was structurally characterized by X-ray single crystal analysis. Compound 2b has been found to be an efficient and reusable catalyst for the alkoxycarbonylation of propylene oxide without the aid of a base additive. The Royal Society of Chemistry.
- Deng, Fan-Guo,Hu, Bin,Sun, Wei,Chen, Jing,Xia, Chun-Gu
-
-
Read Online
- Baeyer-Villiger oxidation of an optically active 1,4-polyketone
-
Baeyer-Villiger oxidation of poly[(S)-2-methyl-1-oxopropane-1,3-diyl] (1) with m-chloroperbenzoic acid provided poly(ketone/ester) (2) in a ratio of ketone/ester = 82/18 in 73% isolated yield. Methanolysis of 2 (Mn = 8600) gave only a trace amount of methyl 3-hydroxybutyrate (5) which resulted from neighboring two ester units, -[OCH(CH3)CH2C(=O)] 2-. The major product was oligoketone CMn = 650). A low yield of 5 indicates that an ester unit likely exists to distribute randomly in 2 rather than to form a block copolymer of a polyketone and a polyester.
- Kosaka, Naoyuki,Hiyama, Tamejiro,Nozaki, Kyoko
-
-
Read Online
- Kinetics of the ring-opening carbonylation of ethyloxirane with hydrido tetracarbonyl cobalt
-
The rate of CO uptake in the reaction of HCo(CO)4 with ethyloxirane, which gives (3-hydroxypentanoyl)cobalt tetracarbonyl as the major product in an n-octane/methyl isobutyl ketone solvent mixture at 15 deg C, is first order with respect to HCo(CO)4 and e
- Kreisz, Jozsef,Ungvary, Ferenc,Sisak, Attila,Marko, Laszlo
-
-
Read Online
- Role of catalyst activation in the enantioselective hydrogenation of methyl acetoacetate over silica-supported nickel catalysts
-
A range of Ni-SiO2 catalysts have been prepared by homogeneous precipitation-deposition and impregnation techniques and modified with aqueous solutions of R-(+)-tartaric acid (TA) to induce enantioselectivity in the asymmetric hydrogenation of a prochiral β-ketoester (methyl acetoacetate) to a β-hydroxyester ((R)-(-)-methyl 3-hydroxybutyrate). The effects of catalyst precursor preparation, nickel loading, and precalcination on the reduction of the precursor were examined and the nature of the resultant nickel particle size distribution is described. The influence of metal-support interactions on the uptake of TA was investigated and data on the corrosive metal leaching and the consequent changes in metal dispersion are presented. Modification of the catalysts with TA not only induced enantioselectivity, but also increased the turnover frequency by up to 15 times that observed for the unmodified surface. The amount of TA adsorbed and the fractional surface coverage by TA is related to the degree of enantiodifferentation. The effects of variations in supported nickel metal particle sizes (in the overall range of 1.4-13.6 nm) on the reaction rate and enantioselectivity were examined; while the selectivity was independent of metal particle size, the rate of hydrogenation was found to be structure sensitive and a correlation between reaction rate sensitivity and particle size is presented.
- Keane
-
-
Read Online
- Process intensification for substrate-coupled whole cell ketone reduction by in situ acetone removal
-
Three different reactor configurations for in situ acetone removal in whole cell biotransformation processes with substrate-coupled cofactor regeneration were applied. The reduction of 2,5-hexanedione to the corresponding (2R,5R)-hexanediol was catalyzed by recombinant Escherichia coli cells expressing an alcohol dehydrogenase from Lactobacillus brevis. The reaction was carried out in a substrate-coupled cofactor regeneration approach using 2-propanol as redox equivalent for intracellular cofactor regeneration. In contrast to a process without acetone removal, where 54% yield could be reached, the yield was increased to >90% when a pervaporation system was applied or when acetone was removed by sparging air through the reaction mixture. In a third system, conversion was driven using a biphasic system to extract acetone continuously from the biocatalyst containing aqueous phase and to allow high concentrations of the hydrophobic substrate 1-phenyl-2-propanone. When methyl tert-butyl ether was applied as the non-aqueous phase, only 24% yield was achieved. When the ionic liquid 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide was applied as the non-aqueous phase, >95% yield was reached as a result of the preferential partitioning behaviour of acetone over 2-propanol into the ionic liquid.
- Schroer, Kirsten,Tacha, Eva,Luetz, Stephan
-
-
Read Online
- HYDROGEN PRESSURE DEPENDENCE OF THE ASYMMETRIC HYDROGENATION OF METHYL ACETOACETATE WITH MODIFIED NICKEL/SiO2 CATALYST
-
The optical yield of methyl 3-hydroxybutyrate in the asymmetric hydrogenation of methyl acetoacetate with tartaric acid-modified Ni/SiO2 catalyst decreased linearly with an increase in the hydrogen pressure up to 10 kg/cm2 in contraast to the data under higher hydrogen pressures.
- Nitta, Yuriko,Sekine, Fumimaro,Sasaki, Jun,Imanaka, Toshinobu,Teranishi, Shiichiro
-
-
Read Online
- Novel solid state reduction of organic functional groups on solid support (Merrifield's resin)
-
Reduction of organic functional groups viz. aldehydes, ketones, esters and epoxides is achieved on solid support in solid state for the first time using NaBH4 and LiAlH4 under solvent free conditions.
- Chandrasekhar,Raza, Abbas,Padmaja
-
-
Read Online
- Thermal decomposition of methyl β-hydroxyesters in m-xylene solution
-
The products and kinetics of the thermal decomposition of several methyl-β-hydroxyesters in m-xylene solution have been studied. It has been shown that all β-hydroxyesters studied pyrolyze to form a mixture of methyl acetate and the corresponding aldehyde or ketone and that the decomposition follows first-order kinetics and appears to be homogeneous and unimolecular. The rate pyrolysis of methyl-3-hydroxypropanoate, methyl-3-hydroxybutanoate, and methyl-3-hydroxy-3-methylbutanoate has been measured between 250 and 320°C. The relative rates of primary, secondary, and tertiary alcohols at 553 K are 1.0. 8.5 and 54.1. respectively. The absence of large substituent effects indicates that little charge separation occurs during the breaking of carbon-carbon single bond. The activation entropy is compatible with a semipolar six-membered cyclic transition state postulated for other β-hydroxy compounds.
- Zapata, Edilma,Gaviria, Jair,Quijano, Jairo
-
-
Read Online
- The Enantioface-differentiating (Asymmetric) Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXIV. The Adsorption Mode of 2-Hydroxy Acid on Raney Nickel
-
The adsorbed species of the modyfying reagent and the surface states of the catalyst caused by the modification of a Raney nickel with 2-hydroxy acid at various pH regions were investigated.The adsorption mode of 2-hydroxy acid was proposed in each modifying-pH region; that is, (1) in a pH region intrinsic to the solution of the free 2-hydroxy acid, nickel salt of 2-hydroxy acid was adsorbed on the catalyst surface corroded by the acid; (2) under weakly acidic conditions, nickel salt and sodium salt of 2-hydroxy acid were adsorbed on the catalyst surface partially corroded by the acid; (3) under neutral conditions, the sodium salt was adsorbed on the surface of the fresh Raney nickel, and (4) under strongly basic conditions, the sodium salt and NaOH were adsorbed on the surface of the fresh Raney nickel.
- Harada, Tadao
-
-
Read Online
- Chemoselective Reduction of Phenyl Ketones with Amino Alcohol-Borane Complexes
-
A new reducing agent was prepared from borane and amino alcohols.The reagent is very effective for chemoselective reduction of ketones in the presence of esters, oxime ethers, tertiary amides, nitriles, halides, and acyl chlorides.The polymeric reagent prepared from borane and polymer-supported amino alcohol was also prepared easily.Aldehydes are highly selectively reduced to primary alcohols in the presence of ketone with the polymeric reagent.Simple filtration separated cleanly the unchanged ketone from the polymeric reagent which gave, after hydrolysis, only primary alcohol as the product.The polymeric reagent was regenerated by treatment with borane and could be reused.
- Itsuno, Shinichi,Wakasugi, Takashi,Ito, Koichi,Hirao, Akira,Nakahama, Seiichi
-
-
Read Online
- Kinetic study of the asymmetric hydrogenation of methyl acetoacetate in the presence of a ruthenium binaphthophosphepine complex
-
The asymmetric hydrogenation of methyl acetoacetate (MAA) in methanol using dibromobis{( S)-4-phenyl-4,5-dihydro-3H-dinaphtho[2,1-c: 1′,2′-e] phosphepine}-ruthenium was studied in detail. For the determination of the reaction network, data from kinetic experiments were compared to different possible reaction networks using the kinetic software Presto Kinetics. The simulation was optimised to describe the reaction accurately with a minimal set of process parameters and reaction equations. For the best model the reaction orders, collision factors and activation energy of all reaction steps were determined. Additionally, the influence of reaction temperature and hydrogen pressure on the enantiomeric excess (ee) of the reaction was studied. It was found that high reaction temperatures and high hydrogen pressures result in increasing enantioselectivities.
- Oechsner, Eva,Etzold, Bastian,Junge, Kathrin,Beller, Matthias,Wasserscheid, Peter
-
-
Read Online
- Challenging the scope of continuous, gas-phase reactions with supported ionic liquid phase (SILP) catalysts - Asymmetric hydrogenation of methyl acetoacetate
-
In the last years Supported Ionic Liquid Phase (SILP) catalysis has attracted growing interest for continuous gas phase reactions. The concept combines in a unique manner the advantages of traditional homogeneous and heterogeneous catalysis by making use of the extremely low vapor pressure of an ionic liquid film on support. In this way, continuous gas phase reactions with macroscopically solid but microscopically homogeneous catalyst materials have been successfully realized. However - so far - continuous gas-phase SILP catalysis has only been demonstrated for reactions with relatively simple selectivity problems (such as, regioselectivity, chemoselectivity). This study demonstrates the successful application of a SILP catalyst in continuous gas phase asymmetric hydrogenation. The hydrogenation of methyl acetoacetate (MAA) is presented using an immobilized dibromo[3-(2,5-(2R,5R)-dimethylphospholanyl-1) -4-di-o-tolylphosphino-2,5-dimethylthio-phene]-ruthenium (Ru1Br2) catalyst.
- ?chsner, Eva,Schneider, Martin J.,Meyer, Carolin,Haumann, Marco,Wasserscheid, Peter
-
-
Read Online
- Ni and Pd mediate asymmetric organoboron synthesis with ester functionality at the β-position
-
Catalytic systems based on Ni and Pd complexes modified with chiral P-P ligands can be used in a convenient strategy for enantioselectively adding a boron unit to the β-position of α,β-unsaturated esters.
- Lillo, Vanesa,Geier, Michael J.,Westcott, Stephen A.,Fernandez, Elena
-
-
Read Online
- A kinetic treatment of heterogeneous enantioselective catalysis
-
Kinetic data are reported for the liquid phase racemic hydrogenation and enantioselective hydrogenation of methyl acetoacetate (MAA) over Ni/SiO2 and tartaric acid (TA)-treated Ni/SiO2, respectively, conducted in a slurry-type reactor. The contribution of mass transport to the overall reaction rate was considered by studying the effects of varying a number of process variables, such as catalyst particle size, catalyst weight, stirring speed and reaction temperature. Reaction conditions are identified wherein contributions due to mass transfer are slight and the hydrogenation proceeds under surface kinetic control. Reaction orders with respect to MAA, hydrogen and the product, methyl 3-hydroxybutyrate (MHB), were determined and activation energies over the temperature range 318 ≤ T ≤ 383 for the bare and TA-modified supported nickel are presented. The reaction rates were observed to pass through maxima as the MAA concentration was increased. The rate data are fitted to a Langmuir-Hinshelwood model where both reactants adsorb competitively on the surface; the experimentally determined rates agree to ±15% with the values predicted by the kinetic model. Modification of the catalyst with TA not only induced enantioselectivity but also promoted the rate of hydrogenation and this effect is discussed in terms of surface interactions and the proposed kinetic model. The ratio of MAA concentration in bulk solution to that at the catalyst surface under reaction conditions is examined and the dependence of enantioselectivity, in the case of the TA-treated sample, on MAA concentration is presented.
- Keane, Mark A.
-
-
Read Online
- On the origin of nitrogen-containing promoters in the cobalt-catalyzed methoxycarbonylation of epoxides
-
The detailed promotion mechanism of nitrogenous compounds in the cobalt-catalyzed methoxycarbonylation of epoxides has not been studied to date. Herein, we present the intrinsic correlation between nitrogenous promoters and activity and selectivity in the alkoxycarbonylation of epoxides by a comprehensive in situ IR spectroscopy and DFT studies. In situ IR spectroscopy confirmed the acid-base neutralization of the nitrogenous promoters and HCo(CO)4, resulting in reduction of the acidity of the catalyst. With the reduced acid-derived activity for formation of ethers as by-products, the selectivity of desired esters was increased. DFT calculations showed that a nitrogenous base could facilitate the methanolysis of cobalt-acyl species with lowered activation energy, which is considered to be the rate-determining step in the catalytic cycle. As a result, the reaction activity towards carbonylation was also improved by nitrogenous promoters. The present studies will provide new insights to the long-term confusing problems in epoxides carbonylation.
- He, Jianghua,He, Lin,Li, Zhen,Liu, Jianhua,Liu, Mengli,Wang, Fang,Xia, Chungu,Yun, Dong,Zeng, Bo
-
-
- Biomimetic ketone reduction by disulfide radical anion
-
The conversion of ribonucleosides to 2′-deoxyribonucleosides is catalyzed by ribonucleoside reductase enzymes in nature. One of the key steps in this complex radical mechanism is the reduction of the 3′-ketodeoxynucleotide by a pair of cysteine residues, providing the electrons via a disulfide radical anion (RSSR??) in the active site of the enzyme. In the present study, the bioinspired conversion of ketones to corresponding alcohols was achieved by the intermediacy of disulfide radical anion of cysteine (CysSSCys)?? in water. High concentration of cysteine and pH 10.6 are necessary for high-yielding reactions. The photoinitiated radical chain reaction includes the one-electron reduction of carbonyl moiety by disulfide radical anion, protonation of the resulting ketyl radical anion by water, and H-atom abstraction from CysSH. The (CysSSCys)?? transient species generated by ionizing radiation in aqueous solutions allowed the measurement of kinetic data with ketones by pulse radiolysis. By measuring the rate of the decay of (CysSSCys)?? at λmax = 420 nm at various concentrations of ketones, we found the rate constants of three cyclic ketones to be in the range of 104–105 M?1s?1 at ~22?C.
- Barata-Vallejo, Sebastian,Bobrowski, Krzysztof,Chatgilialoglu, Chryssostomos,Ferreri, Carla,Marciniak, Bronislaw,Skotnicki, Konrad
-
-
- Discovery of New Carbonyl Reductases Using Functional Metagenomics and Applications in Biocatalysis
-
Enzyme discovery for use in the manufacture of chemicals, requiring high stereoselectivities, continues to be an important avenue of research. Here, a sequence directed metagenomics approach is described to identify short chain carbonyl reductases. PCR from a metagenomic template generated 37 enzymes, with an average 25% sequence identity, twelve of which showed interesting activities in initial screens. Six of the most productive enzymes were then tested against a panel of 21 substrates, including bulkier substrates that have been noted as challenging in biocatalytic reductions. Two enzymes were selected for further studies with the Wieland Miescher ketone. Notably, enzyme SDR-17, when co-expressed with a co-factor recycling system produced the anti-(4aR,5S) isomer in excellent isolated yields of 89% and 99% e.e. These results demonstrate the viability of a sequence directed metagenomics approach for the identification of multiple homologous sequences with low similarity, that can yield highly stereoselective enzymes with applicability in industrial biocatalysis. (Figure presented.).
- Newgas, Sophie A.,Jeffries, Jack W. E.,Moody, Thomas S.,Ward, John M.,Hailes, Helen C.
-
p. 3044 - 3052
(2021/04/26)
-
- A heterogenized cobaltate catalyst on a bis-imidazolium-based covalent triazine framework for hydroesterification of epoxides
-
An imidazolium-cobaltate-based heterogeneous catalyst exhibits advantages over its homogeneous counterpart in the synthesis of β-hydroxyesters from epoxides. However, leaching of cobaltate from the catalytic support decreases the selectivity and recyclability of the catalyst. To overcome such drawbacks, a bis-imidazolium-based covalent triazine framework (CTF) is employed as a catalytic support for the hydroesterification catalyst to reduce cobaltate leaching by the intramolecular anion stabilization effect of the multi-imidazolium moiety, resulting in an excellent selectivity for the β-hydroxyester and unprecedented recyclability.
- Rajendiran, Senkuttuvan,Gunasekar, Gunniya Hariyanandam,Yoon, Sungho
-
p. 12256 - 12262
(2018/07/24)
-
- Enantioselective hydrogenation of ketones over a tartaric acid-modified raney nickel catalyst: Substrate-modifier interaction strength and enantioselectivity
-
Chiral (R,R)-tartaric acid and NaBr-doubly modified Raney nickel (TA-MRNi) is a promising heterogeneous catalyst for enantioselective hydrogenation of prochiral β-keto esters. To obtain deeper insights into the factors ruling the enantioselectivity, enantiodifferentiating hydrogenation of substituted ketones was studied over TA-MRNi and NaBr-modified RNi by use of combined individual-competitive hydrogenation techniques. Relative equilibrium adsorption constants of the substrates were estimated to evaluate their relative interaction strength with adsorbed tartaric acid moiety. DFT calculations were also performed to estimate the interaction energy through hydrogen bonding, providing clear support to the kinetic analysis and surface model. It is concluded with the enantioselective hydrogenation of ketones over TA-MRNi that the enantioselectivity increases as the substrate-modifier interaction strength increases: Methyl acetoacetate (MAA) > acetylacetone (AA) ～ 4-hydroxy-2-butanone (HB) > 2-octanone (2O).
- Choliq, Azka Azkiya,Murakami, Eitaro,Yamamoto, Shota,Misaki, Tomonori,Fujita, Morifumi,Okamoto, Yasuaki,Sugimura, Takashi
-
p. 1325 - 1332
(2018/09/21)
-
- Ionic-Liquid-Based Heterogeneous Covalent Triazine Framework Cobalt Catalyst for the Direct Synthesis of Methyl 3-Hydroxybutyrate from Propylene Oxide
-
β-Hydroxy esters are considered as potential building blocks for the production of fine chemicals and potential drug molecules in various industries. Developing an efficient and recyclable catalyst for the synthesis of β-hydroxy esters is challenging. Her
- Rajendiran, Senkuttuvan,Park, Kwangho,Lee, Kwangyeol,Yoon, Sungho
-
supporting information
p. 7270 - 7277
(2017/06/23)
-
- When Chirality Meets “Buchwald-Type” Phosphines: Synthesis and Evaluation in Frustrated Lewis Pair-, Lewis Base- and Palladium-Promoted Asymmetric Catalysis
-
We describe the synthesis of axially chiral “Buchwald ligand”-like biphenylphosphines in highly enantioenriched form. These monodentate phosphines, biphenyl analogues of Hayashi's MOP ligands, were evaluated in phosphine-promoted organocatalysis and in hydrosilylations catalyzed by palladium or by frustrated Lewis pairs. As expected, the title phosphines appeared best suited for transition metal catalysis where they provided higher asymmetric induction.
- Fer, Micka?l J.,Cinqualbre, Joséphine,Bortoluzzi, Julien,Chessé, Matthieu,Leroux, Frédéric R.,Panossian, Armen
-
p. 4545 - 4553
(2016/09/23)
-
- Immobilization of Carbonylcobalt Catalyst by Poly(4-vinylpyridine) (P4VP) through N→Co Coordination Bonds: The Promotional Effect of Pyridine and the Reusability of Polymer Catalyst
-
A carbonylcobalt catalyst, immobilized by poly(4-vinylpyridine) (P4VP) through N→Co coordination bonds, has been prepared by solvothermal method. It has been revealed that the pyridine fragments in the polymer catalyst act not only as promoters to improve the catalytic performance of the carbonylcobalt catalyst for alkoxycarbonylation of ethylene oxide to methyl 3-hydroxypropanoate but also as stabilizers to enhance the reusability of the polymer catalyst. Furthermore, the polymer catalyst could be easily separated by filtration and reused with only a slight loss of catalytic efficiency.
- Liu, Yu-Bing,Wang, Yi-Ning,Lu, Hai-Meng,Liang, Shuang,Xu, Bo-Lian,Fan, Yi-Ning
-
supporting information
p. 3159 - 3164
(2016/11/29)
-
- Cobalt oxide supported gold nanoparticles as a stable and readily-prepared precursor for the in situ generation of cobalt carbonyl like species
-
A treatment of cobalt oxide supported gold nanoparticles (Au/Co 3O4) under syngas atmosphere effectively generated a cobalt carbonyl-like active species in the reaction vessel. The preparation of Au/Co3O4 was quite simple and the in situ generated cobalt species could be used as a stable and easy handling alternative for dicobalt octacarbonyl without bothersome purification prior to use. The reactions, which are sensitive to the purity of the dicobalt octacarbonyl, such as the alkoxycarbonylation of epoxides and the Pauson-Khand reaction, smoothly progressed with Au/Co3O4.
- Hamasaki, Akiyuki,Muto, Akiko,Haraguchi, Shingo,Liu, Xiaohao,Sakakibara, Takanori,Yokoyama, Takushi,Tokunaga, Makoto
-
supporting information; experimental part
p. 6869 - 6872
(2012/02/05)
-
- Reduction processes biocatalyzed by Vigna unguiculata
-
Whole cells from the Brazilian beans feijao de corda (Vigna unguiculata) have been employed as biocatalysts in different bioreduction processes. Good to excellent selectivities can be obtained in the reduction of aromatic and aliphatic ketones, as well as β-ketoesters, depending on the conversions and the chemoselectivity on the substrate structure. This biocatalyst was also able to reduce the nitro moiety of different aromatic nitro compounds, showing as well enoate reductase activity, and chemoselectively catalyzing the double bond reduction of 4-phenyl-3-buten-2-one with moderate conversion.
- Bizerra, Ayla M.C.,Gonzalo, Gonzalo de,Lavandera, Ivan,Gotor-Fernandez, Vicente,de Mattos, Marcos Carlos,de Oliveira, Maria da Conceicao F.,Lemos, Telma L.G.,Gotor, Vicente
-
experimental part
p. 566 - 570
(2010/08/06)
-
- Chirally functionalized mesoporous organosilicas with built-in BINAP ligand for asymmetric catalysis
-
The chirally functionalized periodic mesoporous organosilica (PMO) with C2-symmetric chiral building blocks, BINAP (2,2′- bis(diphenylphosphino)-1,1′-binaphthyl), in the pore wall was successfully synthesized for the first time using a successive co-condensation and post-synthesis modification method. Chiral BINAPO (2,2′- bis(diphenylphosphinooxide)-1,1′-binaphthyl) bridging mesoporous organosilica with highly ordered 2-D hexagonal structure was first synthesized by co-condensation of (R)-5,5′-bis(3-triethoxysilylpropyl-1-ureyl)-2, 2′-bis(diphenylphosphinooxide)-1,1′-binaphthy with tetramethoxylsilane in the presence of block copolymer P123 as template under weakly acidic conditions. The BINAPO in the pore wall of PMO was reduced with trichlorosilane to generate BINAP using a post-synthesis modification method. The chiral PMO with built-in BINAP (coordination with [RuCl2- (benzene)]2) is an efficient solid catalyst for the asymmetric hydrogenation of β-keto esters with ee as high as 99%, which is among the highest ever reported for the chirally functionalized PMOs in asymmetric catalysis.
- Wang, Peiyuan,Liu, Xiao,Yang, Jie,Yang, Yan,Zhang, Lei,Yang, Qihua,Li, Can
-
scheme or table
p. 8009 - 8014
(2010/06/13)
-
- Axially 4,4′-di-tert-butyl TunePhos-type chiral diphosphine ligand: synthesis and applications in asymmetric hydrogenation
-
Axially 4,4′-di-tert-butyl TunePhos-type chiral diphosphine ligand was designed and synthesized by means of central-to-axial chirality transfer. Up to 99% and 98% ee have been achieved in Ru-catalyzed hydrogenation of β-alkyl and β-aryl-substituted β-keto esters, respectively.
- Wang, Chun-Jiang,Wang, Chu-Bei,Chen, Dong,Yang, Guangfu,Wu, Zhengshun,Zhang, Xumu
-
scheme or table
p. 1038 - 1040
(2009/05/31)
-
- HYDANTOIN DERIVATIVES USEFUL AS ANTIBACTERIAL AGENTS
-
This invention relates to compounds of the Formula (I): or a pharmaceutically acceptable salt, solvate, ester or isomer thereof, which is useful for the treatment of diseases or conditions mediated by LpxC.
- -
-
Page/Page column 66-67
(2008/06/13)
-
- Methods for preparing 3-hydroxy-propionate and 1,3-propylene glycol
-
The invention disclosed a method for producing 3-hydroxy-propionate and 1,3-propylene glycol by using epoxide as raw material. In the method, a transitional metal cobalt catalyst and a cocatalyst for the hydroesterification reaction among epoxide, carbon monoxide, and alcohol were chosen, and a hydrogenation catalyst for hydrogenating 3-hydroxy-propionate as well as the corresponding process conditions were selected for producing 3-hydroxy-propionate and 1,3-propylene glycol.
- -
-
Page/Page column 4-5
(2008/06/13)
-
- Carbonylative ring opening of terminal epoxides at atmospheric pressure
-
(Chemical Equation Presented) The carbonylative opening of terminal epoxides under mild conditions has been developed using Co2-(CO) 8 as the catalyst. Under 1 atm of carbon monoxide and at room temperature in methanol, propylene oxide is converted to methyl 3-hydroxybutanoate in up to 89% yield. This transformation is general for many terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, chloromethyl, phthalimido, and acetal functional groups. The opening takes place without epimerization at the secondary stereocenter.
- Denmark, Scott E.,Ahmad, Moballigh
-
p. 9630 - 9634
(2008/03/17)
-
- Selective transfer hydrogenation of carbonyl compounds by ruthenium nanoclusters supported on alkali-exchanged zeolite beta
-
Selective transfer hydrogenation of aromatic ketones and β-keto esters to the corresponding alcohols was achieved by using ruthenium nanoclusters supported on alkali-exchanged zeolite beta catalyst. The high activity and selectivity of the catalyst is due to the presence of highly dispersed ruthenium clusters in combination with the large number of Bronsted acidic sites of zeolite.
- Kantam, M. Lakshmi,Rao, B. Purna Chandra,Choudary,Sreedhar
-
p. 1970 - 1976
(2007/10/03)
-
- Fast aqueous/organic hydrogenation of arenes, olefins and carbonyl compounds by poly(N-vinylpyrrolidone)-Ru as amphiphilic microreactor system
-
Fast aqueous/organic hydrogenations of arenes, olefins and carbonyl compounds were successfully realized in a PVP-Ru amphiphilic microreactor system. The turnover frequency (TOF) of aqueous/organic hydrogenation of benzene reached 45,000 h-1. All the hydrogenation TOFs of investigated benzene derivatives, olefins and carbonyl compounds exceeded 1000 h -1.
- Lu, Fang,Liu, Jing,Xu, Jie
-
p. 857 - 861
(2007/10/03)
-
- PROCESS FOR PRODUCING AMINO ACID DERIVATIVES
-
The present invention relates to a process for producing amino acid derivatives such as optically active β-amino acid in short steps with good yield and high optical purity, which comprises reacting a keto acid of the formula (1): wherein R1 is hydrogen, an optionally substituted hydrocarbon, etc.; R2 is a spacer; and R3 is an optionally substituted alkoxy, etc., or a salt thereof, with ammonia or an amine or a salt thereof in the presence of a chiral catalyst and in the presence or absence of an acid and/or a fluorine-containing alcohol, to give an amino acid derivative of the formula (2): wherein Q is a group formed by removing one hydrogen atom from ammonia or an amine; X' is an acid and/or a fluorine-containing alcohol; and b is 0 or 1.
- -
-
Page/Page column 49-50
(2008/06/13)
-
- Synthesis of isotetronic acids by cyclization of 1,3-bis(trimethylsilyloxy) alk-1-enes with oxalyl chloride
-
Isotetronic acids were regioselectively prepared by cyclization of 1,3-bis(trimethylsilyloxy)alk-1-enes with oxalyl chloride.
- Dede, Rüdiger,Michaelis, Lars,Langer, Peter
-
p. 8129 - 8131
(2007/10/03)
-
- Chiral porous metal phosphonates for heterogeneous asymmetric catalysis
-
Chiral porous zirconium phosphonates containing metal complex moieties are provided, synthesized via a molecular building block approach, and characterized by a variety of techniques including TGA, adsorption isotherms, XRD, SEM, IR, and microanalysis. These hybrid solids may be used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with remarkably high e.e. values of up to 99.2%. Similarly prepared chiral porous solids may be used for asymmetric hydrogenation of β-keto esters with e.e.'s of up to 95%. The solid catalysts can also be easily recycled and reused multiple times without the loss of activity and enantioselectivity. Ready tunability of such a molecular building block approach allows the optimization of these hybrid materials to provide practically useful heterogeneous asymmetric catalysts.
- -
-
Page/Page column 12
(2010/02/08)
-
- Mesoporous silica anchored Ru catalysts for highly enantioselective hydrogenation of β-ketoesters
-
Recyclable and reusable mesoporous silica anchored Ru catalysts based on 4,4′-substituted BINAPs were synthesized and used for the hydrogenation of β-alkyl β-ketoesters with up to 98.6% e.e. and β-aryl β-ketoesters with up to 95.2% e.e.
- Kesanli, Banu,Lin, Wenbin
-
p. 2284 - 2285
(2007/10/03)
-
- Polyhydroxyalkanoate and manufacturing method thereof
-
To provide a novel polyhydroxyalkanoate and a manufacturing method by a microorganism capable of substantially reducing unintended monomer units and obtaining the polyhydroxyalkanoate in a high yield. A microorganism capable of synthesizing a novel polyhydroxyalkanoate having 3-hydroxy-substituted benzoylalkanoic acid as a monomer unit using a substituted benzoylalkanoic acid as a material is cultured in the medium containing a substituted benzoylalkanoic acid, then the polyhydroxyalkanoate produced in the cultured bacteria is extracted and recovered.
- -
-
Page/Page column 35-36
(2008/06/13)
-
- Sodium borohydride reduction and selective transesterification of β-keto esters in a one-pot reaction under mild conditions
-
An efficient and simple one-pot method of preparing β-hydroxy esters by sodium borohydride reduction cum selective transesterification of β-keto esters under mild conditions is described.
- Padhi, Santosh Kumar,Chadha, Anju
-
p. 639 - 642
(2007/10/03)
-
- Highly enantioselective catalytic asymmetric hydrogenation of β-keto esters in room temperature ionic liquids
-
Polar phosphonic acid-derived Ru-BINAP systems were used to catalyze asymmetric hydrogenation of β-keto esters in room temperature ionic liquids (RTILs) with complete conversions and ee values higher than those obtained from homogeneous reactions in MeOH (up to 99.3%), and were recycled by simple extraction and used for four times without the loss of activity and enantioselectivity.
- Ngo, Helen L.,Hu, Aiguo,Lin, Wenbin
-
p. 1912 - 1913
(2007/10/03)
-
- Direct Zn-diamine promoted reduction of C=O and C=N bonds by polymethylhydrosiloxane in methanol
-
Ketones and imines are chemoselectively reduced at room temperature in methanol to the corresponding alcohols and amines in high yields in a one-step procedure using polymethylhydrosiloxane (PMHS) and a simple zinc-diamine catalyst.
- Bette, Virginie,Mortreux, Andre,Lehmann, Christian W.,Carpentier, Jean-Francois
-
p. 332 - 333
(2007/10/03)
-
- Novel coumarin and chromene compounds and methods of preparation and use thereof for treating or preventing viral infections
-
The present invention relates to methods of preparation and use of coumarin and chromene compounds for treating or preventing viral infections.
- -
-
-
- Process for preparing 1,3-alkanediol from epoxide derivative
-
A process for preparing an 1,3-alkanediol through carbonylation of an epoxide derivative includes the steps of (a) reacting an epoxide derivative with alcohol and carbon monoxide in a solvent at a temperature from about 30 to about 150° C. and at a pressure from about 50 to about 3000 psig in the presence of a catalyst system including an effective amount of a cobalt catalyst and an effective amount of a promoter to afford a reaction mixture including a 3-hydroxyester or derivative thereof in an amount of from 2 to about 95% by weight, (b) separating the reaction product and solvent from the catalyst and promoter, (c) reacting said reaction product and solvent with hydrogen at a temperature from about 30 to about 350° C. and at a pressure from about 50 to about 5000 psig in the presence of a catalyst system for hydrogenation to prepare a hydrogenation product mixture including a 1,3-alkanediol, and (d) recovering the 1,3-alkanediol from the hydrogenation product mixture. Catalyst systems for carrying out the inventive processes are also provided.
- -
-
Page column 9
(2008/06/13)
-
- Over 98% optical yield achieved by a heterogeneous catalysis. Substrate design and analysis of enantio-differentiating factors of tartaric acid-modified Raney nickel hydrogenation
-
Tartaric acid-modified Raney nickel (TA-MRNi) is a chiral heterogeneous catalyst for the hydrogenation of prochiral ketones. An optical yield (OY) of 86% with methyl acetoacetate (1) as a substrate was improved to 94-96% by employing β-keto esters having a proper bulkiness at the γ-position. The γ-bulkiness effect contributes to a high intrinsic enantio-differentiating ability (factor-i) of the TA-MRNi catalysis. Through the study, we found the best substrate, γ-cyclopropyl-β-keto ester, the hydrogenation of which resulted in 98.6% OY. This further improvement in the OY was ascribed to a smaller contribution of non-enantio-differentiating hydrogenation (N-site catalysis) due to the substrate-specific activation of the enantio-differentiating hydrogenation by the chiral modifier. The OY of the hydrogenation of 1 was analyzed by comparing with well-behaved β-keto esters, and the contribution of the factor-i and the N-site to the OY value was evaluated to deduce the origin of the enantiodifferentiation.
- Sugimura, Takashi,Nakagawa, Satoshi,Tai, Akira
-
p. 355 - 363
(2007/10/03)
-
- Reduction of ketones and alkyl iodides by Sml2 and Sm(ii)-HMPA complexes. Rate and mechanistic studies
-
The effect of HMPA on the electron transfer (ET) rate of samarium diiodide reduction reactions in THF was analyzed for a series of ketones (2-butanone, methyl acetoacetate, and N,N-dimethylacetoacetamide) and alkyl iodides (1-iodobutane and 2-iodobutane) with stopped flow spectrophotometric studies. Activation parameters for the ET processes were determined by temperature-dependence studies over a range of 30-50 °C. The ET rate constants and the activation parameters obtained for the above systems in the presence of different equivalents of HMPA were compared to understand the mechanism of action of HMPA on various substrates. The results obtained from these studies indicate that coordination or chelation is possible in the transition state geometry for Sml2/ketone systems even in the presence of the sterically demanding ligand HMPA. After the addition of 4 equiv of HMPA the ET rate and activation parameters for ketone reduction by Sm is unaffected by further HMPA addition while a linear dependence of ET rate on the equivalents of HMPA was found in the Sml2/alkyl iodide system. The results of these studies are consistent with an inner-sphere-type ET for the reduction of ketones by Sml2 (and Sml2-HMPA complexes) and an outer-sphere-type ET for the reduction of alkyl iodides by Sml2 or Sml2-HMPA complexes.
- Prasad,Flowers II, Robert A.
-
p. 6895 - 6899
(2007/10/03)
-
- Mechanistic study of β-substituent effects on the mechanism of ketone reduction by Sml2
-
The rate constants for the reduction of 2-butanone, methylacetoacetate, N, N-dimethylacetoacetamide, and a series of 4′- and 2′-substituted acetophenone derivatives by Sml2 were determined in dry THF using stopped-flow absorption decay experiments. Activation parameters for the electron-transfer processes in each series of compounds were determined by a temperature-dependence study over a range of 30 to 50 °C. Two types of reaction pathways are possible for these electron-transfer processes. One proceeds through coordination (Scheme 1) while the other involves chelation (Scheme 2). The results described herein unequivocally show that both coordination and chelation provide highly ordered transition states for the electron-transfer process but the presence of a chelation pathway dramatically increases the rate of the reduction of these substrates by Sml2. The ability of various functional groups to promote a chelated reaction pathway plays a crucial role in determining the rate of the reaction. Among the 2′-substituted acetophenone series, the presence of a fluoro, amino, or methoxy substituent enhances the rate of reduction compared to the 4′-analogues. In particular, the presence of a 2′-fluoro substituent on acetophenone provides a highly ordered transition state and considerably enhances the rate of ketone reduction.
- Prasad, Edamana,Flowers II, Robert A.
-
p. 6357 - 6361
(2007/10/03)
-
- Methods for preparing antiviral calanolide compounds
-
The present invention relates to methods for preparing 2,2-dimethyl-5-acyloxy-10-propyl-2H,8H-benzo[ 1,2-b:3,4-b ′]dipyran-8-one (5) and 2,2-dimethyl-5-hydroxy- 10-propyl-2H,8H-benzo[1,2-b:3,4-b ′]dipyran-8-one (6) and their use as intermediates for the synthesis of antiviral calanolide compounds. For example, Fries rearrangement on compound 5 or Friedel-Crafts reaction on 6, yields intermediate 2,2-dimethyl-5-hydroxy-6-propionyl-10-propyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-8-one (4), which, in turn, can be converted to (+)-calanolide A and (?)-calanolide B. The coupling of compound 6 with the appropriate chiral molecule under Mitsunobu or nucleophilic displacement leads to the asymmetric synthesis of antiviral calanolide compounds.
- -
-
-
- A mild and effective method for the transesterification of carboxylic acid esters
-
An extraordinarily versatile transesterification of simple or highly functionalized esters of aliphatic and aromatic carboxylic acids in high yields is catalyzed by dibutyltin oxide [Eq. (1)]. The reaction is compatible with several functional groups, for example, acetals, ketals, aliphatic bromides, enol ethers, urethanes, as well as free hydroxy, phenolic, and amino groups, and even with water.
- Baumhof, Patrick,Mazitschek, Ralph,Giannis, Athanassios
-
p. 3672 - 3674
(2007/10/03)
-
- Elucidation of mechanism of inhibition and X-ray structure of the TEM-1 β-lactamase from Escherichia coli inhibited by a N-sulfonyloxy-β-lactam
-
Class A β-lactamase are inactivated by a novel type of monocyclic ?- lactams described recently (J. Am. Chem. Soc. 1995, 117, 5938). A compound of this class, (±)-trans-1-N-(tosyloxy)-3-(1-hydroxyethyl)-4-phenyl-2- azetidinone, is synthesized, is shown to acylate the active site of the TEM- 1 β-lactamase from Escherichia coli rapidly, and resists deacylation for several days. The crystal structure of the enzyme-inhibitor complex was determined at 1.95 A? resolution. The features of the three-dimensional structure of this acyl-enzyme species and mechanistic studies revealed that a fragmentation of the inactivation ensued on acylation of the active-site serine and that the ester carbonyl oxygen was outside the oxyanion hole. This ester carbonyl makes a strong hydrogen bond to the protonated form of the side chain of Glu-166, the general base for deacylation of the typical acyl- enzyme intermediates in the normal catalytic process. Furthermore, interactions within the active site mandated the existence of the former β- lactam amine as an imine or a ketone, and not as an enamine or an enol, and shed light on the unique mechanism of action of these enzyme inactivators. This type of inactivator holds the promise of application for inhibition of other enzymes.
- Swarén, Peter,Massova, Irina,Bellettini, John R.,Bulychev, Alexey,Maveyraud, Laurent,Kotra, Lakshmi P.,Miller, Marvin J.,Mobashery, Shahriar,Samama, Jean-Pierre
-
p. 5353 - 5359
(2007/10/03)
-
- Ruthenium-phosphine complex
-
A novel ruthenium-phosphine complex useful as a catalyst for asymmetric hydrogenation is disclosed, which is represented by formula (I): wherein Et stands for an ethyl group; and R-BINAP represents a tertiary phosphine represented by formula (II): STR1 wherein R represents a hydrogen atom or a methyl group.
- -
-
-
- Ferrocene diphosphines as ligands for homogeneous catalysts
-
Compounds of the formula I STR1 wherein R1 is C1 -C8 alkyl, phenyl or phenyl which is substituted by 1 to 3 C1 -C4 alkyl or C1 -C4 alkoxy groups; R2 and R3 are each independently of the other typically C1 -C12 alkyl, C5 -C12 cycloalkyl, phenyl, or C1 -C4 alkyl- or C1 -C4 alkoxy-substituted C5 -C12 cycloalkyl, or phenyl which is substituted by one to three identical or different members selected from the group consisting of C1 -C4 alkyl, C1 -C4 alkoxy or halogen; R10 and R11 are identical and are typically C1 -C12 alkyl, C5 -C12 cycloalkyl, C1 -C4 alkyl- or C1 -C4 alkoxy-substituted C5 -C12 cycloalkyl or phenyl which is substituted by 1 to 3 identical or different members selected from the group consisting of C1 -C4 alkyl, C1 -C4 alkoxy or halogen; or R10 and R11 are different and are C1 -C12 alkyl, C5 -C12 cycloalkyl, C1 -C4 alkyl- or C1 -C4 alkoxy-substituted C5 -C12 cycloalkyl, phenyl or phenyl which is substituted by 1 to 3 identical or different members selected from the group consisting of C1 -C4 alkyl, C1 -C4 alkoxy or halogen, and * denotes a stereogenic carbon atom, in the form of their racemates and diastereoisomers or mixtures of diastereoisomers. Rhodium and iridium complexes with these ligands are suitable for use as homogeneous enantioselective catalysts for the hydrogenation of prochiral compounds containing carbon double bonds or carbon/hetero atom double bonds.
- -
-
-
- Chemo- and Regioselective Reductions of Functionalized Epoxides by Bu3SnH/Bu3SnI-Phosphine Oxide
-
A novel reagent, Bu3SnH/Bu3SnI-phosphine oxide, reduced functionalized epoxides to the corresponding alcohols in high chemo- and regioselectivities.
- Kawakami, Takayo,Tanizawa, Daisuke,Shibata, Ikuya,Baba, Akio
-
p. 9357 - 9360
(2007/10/02)
-
- Reactions of β-Lactones with Potassium Alkoxides and Their Complexes with 18-Crown-6 in Aprotic Solvents
-
The mechanism of the reaction of β-lactones (2-oxetanones) with potassium alkoxides in aprotic solvents was investigated.Despite previous suggestions, the attack of alkoxide ion occurs on the carbonyl carbon atom of β-lactones, cleaving the acyl-oxygen bond to yield the corresponding potassium alcoholate of the respective β-hydroxycarboxylic acid ester.Next, the unsaturated ester is formed due to potassium hydroxide elimination.The nature of the alkoxide used and complexation of alkali metal cation by crown ether have no significant effect on the reaction course in aprotic solvents.
- Kurcok, Piotr,Jedlinski, Zbigniew,Kowalczuk, Marek
-
p. 4219 - 4220
(2007/10/02)
-
- Optical Resolution of Amino Acid and Hydroxycarboxylic Acid Esters by Complexation with Optically Active Host Compounds: a Crystallographic Result
-
Selected esters derived from amino and hydroxycarboxylic acids have been resolved by inclusion complexation with optically active host compounds derived from tartaric acid.The crystal structure of the inclusion compound I (R,R)-(-)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4-dioxaspirononane-*1/2(methyl 3-hydroxybutanoate) is reported.I is monoclinic P21, a = 9.176(2), b = 39.70(2), c = 9.216(2) Angstroem, β = 119.45(1) deg, V = 2923(2) Angstroem3.The structure was solved by direct methods and refined to a final R value of 0.037.Host and guest molecules are linked by hydrogen bonding.
- Toda, Fumio,Sato, Atsushi,Nassimbeni, Luigi R.,Niven, Margaret L.
-
p. 1971 - 1976
(2007/10/02)
-
